There is a national interest in the discovery of alternative sources of fuels and chemicals, other than from petroleum resources. As the public discussion concerning the availability of petroleum resources and the need for alternative sources continues, it is anticipated that future government mandates will require transportation fuels to include, at least in part, hydrocarbons derived from sources besides petroleum. As such, there is a need to develop alternative sources for hydrocarbons useful for producing fuels and chemicals.
One possible alternative source of hydrocarbons for producing fuels and chemicals is the natural carbon found in plants and animals, such as for example, in the form of carbohydrates. These so-called “natural” carbon resources (or renewable hydrocarbons) are widely available, and remain a target alternative source for the production of hydrocarbons. For example, it is known that carbohydrates and other sugar-based feedstocks can be used to produce ethanol, which has been used in gasohol and other energy applications. However, the use of ethanol in transportation fuels has not proven to be cost effective.
Carbohydrates, however, also can be used to produce fuel range hydrocarbons. The upgrading of biologically derived materials to materials useful in producing fuels is known in the art. However, many carbohydrates (e.g., starch) are undesirable as feed stocks due to the costs associated with converting them to a usable form. In addition, many carbohydrates are known to be “difficult” to convert due to their chemical structure, or that the hydrocarbon product produced is undesirable or will result in low quantities of desirable product. Among the compounds that are stated to be difficult to convert include compounds with low effective hydrogen to carbon ratios, including carbohydrates such as starches and sugars, carboxylic acids and anhydrides, lower glycols, glycerin and other polyols and short chain aldehydes. As such, efforts have been made to convert traditionally difficult to convert materials to hydrocarbons by focusing on methods for increasing the effective hydrogen to carbon ratio of the reactants, including converting oxygenates in the presence of hydrogen, CO, steam, nitrogen, or other reactants, and by employing various catalysts. However, these processes are often complex and are costly, and the reaction products produced as a result of these processes are oftentimes undesirable, or result in low weight percentages, and often result in an increase in undesirable byproducts such as the production of carbon monoxide and carbon dioxide.
In addition, many carbohydrates (such as complex polysaccharides, including corn starch) in their raw form are undesirable as feeds. For example, starch, in its native form, is a solid and as such, prior to use, it is desirable to convert the solid form into a liquid form for ease of processing. However, when starch is combined with liquid, it becomes extremely viscous, making dissolution difficult. As a result, many processes employed only result in the partial hydrolyzation of the carbohydrate starting material, which necessitates addressing the undissolved solid fraction in the reaction zone. In addition, because of the viscosity, it is often required to mix the carbohydrate with large volumes of water and/or chemicals, along with harsh reaction conditions in order to achieve the desired dissolution.
As such, development of a process for increasing the solubility of carbohydrates in the conversion of carbohydrates to hydrocarbons would be a significant contribution to the art. In addition, development of a process for converting carbohydrates to hydrocarbons which yields significant quantities of desirable hydrocarbon products such as aromatics and olefins would be a significant contribution to the art. Furthermore, development of a carbohydrate conversion process resulting in a product with reduced byproducts such as carbon monoxide and carbon dioxide, and coke production, would be a significant contribution to the art.